Immunoglobulins (antibodies)

IgG

• Found in blood

• Active against bacteria, bacterial toxins, and viruses

• Activates complement system

• Only antibody to cross placental barrier

• Important in secondary immune response

IgA

• Found in saliva, tears, breast milk, blood, and secretions

• Provides local protection on exposed mucous membranes

• Prevents virus cells from binding to respiratory & GI tracts

IgM

• Found in blood and lymph

• 1st antibody produced in primary immune response

• Activates complement

• High initial concentration

• 1st to arrive at the site of attack

IgD

• Found in blood, lymph, and on B cells

• May have role in keeping immune system under control

IgE

• Found in mast cells and basophils

• Triggers release of histamine from mast cells

• Associated with allergies